Marit Bjoergen already has enough Olympic gold medals for her own collection. This one was for her grieving teammate.

Bjoergen won the women's 15-kilometer skiathlon in the opening cross-country event at the Sochi Olympics on Saturday to earn her fourth career gold on an emotional day for the close-knit Norwegian team. It was dealing with the news that Astrid Uhrenholdt Jacobsen's brother had died a day earlier.

Bjoergen and her three teammates — who also finished third and fourth — broke down in tears as they embraced immediately after the race, and she dedicated the victory to Jacobsen's family.

"Astrid and her family wanted us to race for her brother, and we really did a good race for him today," Bjoergen said. "Of course it is emotional. We did it for her, her family and her brother."

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The Norwegian Olympic team said Jacobsen's brother died "suddenly and unexpectedly" on Friday, but did not provide any details.

Heidi Weng won the bronze medal with teammate Therese Johaug in fourth. Charlotte Kalla of Sweden prevented a Norwegian medal sweep by taking the silver after a two-way contest against Bjoergen in the stadium.

Bjoergen held off Kalla on the final straight to win in 38 minutes, 33.6 seconds and defend her title from the 2010 Vancouver Games. Kalla was 1.8 seconds behind.

Weng won a three-way sprint for the bronze medal, coming 13.2 seconds behind the Bjoergen. During the flower ceremony on the podium, both Bjoergen and Weng were in tears and Weng was still crying when talking to reporters.

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"Today I go for Astrid and I promised her to go fast," said Weng, a 22-year-old who was making her first Olympic start. "I had more power today to go for Astrid."

Bjoergen entered the race as a big favorite and didn't disappoint. She was the most successful athlete of the Vancouver Games with three gold medals, a silver and a bronze, and she showed right away she has the ability to match that feat in Sochi.

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Having said this week she'd be happy with only one gold, she now has to set a more ambitious target.

"One gold was my goal, so now I can relax a little bit," Bjoergen said. "I think anything is possible."

With a group of five skiers staying together until the last kilometer, Kalla tried to pull away in the final uphill section before the sprint. Only Bjoergen was able to match her pace going up the hill, and Kalla then had no answer for the Norwegian's strong finish.

"I knew Charlotte would be strong in the sprint and she's good at the climbs but I thought that if I could follow her, I would have a chance," Bjoergen said.

At 33 years and 324 days, Bjoergen became the oldest woman to win an individual Olympic cross-country gold, beating Stefania Belmondo's record of 33 years and 27 days. The Italian won the 15K freestyle at the 2002 Salt Lake City Games. She also became her country's most successful female Olympian of all time, having shared the record with figure skater and actress Sonja Henie, who won three golds between 1928 and '36.

The skiathlon event starts with 7.5 kilometers of classical-style skiing before switching to freestyle, making it a tough test of the athletes' all-round abilities.

Kalla won the 10K freestyle event in Vancouver and showed she has vastly improved her classical style since then. She has never finished on the podium in a skiathlon on the World Cup circuit, and her celebration Saturday — raising her arms as she crossed the line behind Bjoergen and then jumping up and down holding her skis in the air — looked as if she had won.

"It means a lot to me to be on the podium for the first time. I could not imagine this before the race," Kalla said.

Jessica Diggins of the United States finished eighth in her first Olympic start.

Justyna Kowalczyk of Poland, a three-time overall World Cup champion who has been struggling with a foot injury, was with the leading group of seven skiers at the halfway mark but slipped and fell as she was about to enter her station for the ski change. She lost several seconds.

She fell further behind in the freestyle portion and finished sixth, 58.1 seconds back.